Air bag treatment



Patented Jan. 21, 1941 o 2,229,579

UNITED STATES rTsuT rrr-cs AIR BAG TREATMENT Frank H. Manchester, Akron, Ohio, assigner to Wingfoot Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application August 1, 1936, Serial No. 93,886

This invention relates to improvements in the C. and preferably not exceeding 10 below zero vulcanization of rubber and concerns particu- C. and especially at between 40 to 80 below larly cores or bags inserted within hollow articles Zero C. with a catalyst of the Friedel-Crafts such as pneumatic tires for molding and curing type such as boron uoride, although aluminum purposes, and particularly those bags which are chloride, titanium tetra chloride, and the like may '5i made of rubber and filled with air, or a gas or also be used in many cases. The molecular fluid such as steam or Water which may be heated. weight of the polymer is, generally speaking, con- In the vulcanization of pneumatic tires and the trolled by the purity of the unsaturated hydrolike such cores or curing bags have been found to carbon, the catalyst and the temperature of polydeteriorate during use particularly on their inner merization. The higher polymers are obtained 10 surfaces. Where air is used the deterioration at very low temperatures and with very pure oleseems to be caused principally by heat and oxifins. dation. Various compositions have been used These pelymers are characterized by a high heretofore to protect the surfaces of such bags viscosity over a Wide range 0f temperatures.

when used for curing tires and other articles They also have goed adhesive properties and are 15 with air under pressure in the curing bag. Illushighly resistant to oxidation. Thus, they will trative are the glycerine compositions disclosed adhere t0 the inner Surface Of the Curing bag in U S Patents Nos, 1,755,069 and 1,694,379 and will retain a suiliciently high viscosity at tem- Where steam or water is the inilating medium perf-times up i0 about 125 C. t0 prevent iOWilg employed in the Curing nog, glycerin@ oomposito such an extent that the inner surface of the 20 tions have not been satisfactory because of the beg iS eXDo-Sed. fact that they distill on with the steam or are These polymers Without any additive material otherwise carried away by the steam or the'water. may be iniredU-Ced into the curing bag during iiS Without a proteetant the interior of the bag cormanufacture and before it is spliced, 0r Jthey may rodes 01' OXdjZes 0r @Todes S0 that pieces 0f the be ClSSOll/Sd With /SOlVel'll Such as CalbOIl tetra, 25 interior portion of the bag brook off in segments chloride or a water emulsion can be made using of the nature of coiee grounds. The bag fails casein as a protective colloid, and the solution by becoming prcgressive1y thinner as the oxidoor emulsion added to the air bag inner surface. tion or erosion process goes on These solutions or emulsions of the polymer may Itis, accordingly, an object of this invention to then be Deiiiied 0D the inner surface of the cur- 30 provide a composition which when injected or ing beg 01, if SllliCerlly dilute, they may be i11- otherwise inserted into a curing bag will pre- J'eCteOl tliIOugh the Curing beg Valve stem. serve the inner surfaces thereof against the SaiSfCiOTY YeSlllS @Je Obtained by this DIO- action of steam, carbon dioxide, air, hot water, Cedue but Very mlleh more SeiSfaCiOly eSillS and other deteriorating influences or combinaare Obtained by using a mixture of polymorizod 35 tions of those guido Another ohjoofl is to proisobutylene with a relatively nonoxidizable plas- Vido an improved oulihg nog other objects will ticizing material which is compatible with the become apparent as the description of the inven- Polymerized isobutylene. Illustrative of such tion proooods t non-oxidizable materials are paraffin, rosin, bees- 40 The invention involves the discovery that com- Wa-X, Camallba WaX, HeilOWaX (chlorinated Heph- 40 positions Comprising high molecular polymers of thalenes), cumar and Arochlors (halogenated purely aliphatic mono olens having branched Cliphenyls). Of these non-oxidizable materials, carbon chains, more particularly of isobutylene, pal'a'n S Dlefelrefl- Palain and these other are excellent agents for preventing the deteri- WaXy 01 reSIlOllS meterelS, besides acting as e omi-,ion of oir bags duo to the harmful action plasticizer for the polymerized isobutylene, have 45 0f the inflating mediums employed. the property of preserving the inner surfaces of The polymers used according to this invention ail' bags by themselves and also aid in keeping are materials having a Vor-y high moieoular the air bag flexible and pliable. However, by weight, usually of at least about 1G00 and ranging themseles they Will 110i adhere t0 they bag surupto a Vahle ih the neighborhood of 10,000 and face. Also, most of them are absorbed by the v50 even much higher, depending on the manner in l'ubbel t@ Some extent- Whioh they are proporod Such polymers may The polymerized isobutylene besides being a be obtained by polymerizing unsaturated hydro- DleSelVing agent itself Will adhere to the rubcarbons such as isobutylene, Polymerization bel' Surface and Will also inhibit the abSOIpll'On may be carried out at temperatures below zero of the waxy material by the rubber. The non- 55 oxidizable waxy or resinous material renders the polymerized isobutylene more plastic and more readily applicable to the curing bag. Thus, a mixture of polymerized isobutylene and a nonoxidizable waxy or resinous material heated to about C. can be easily injected into the curing bag through the valve stem, no solvents or other thinners being necessary.

The polymerized isobutylene applicable for use in the practice of the invention may vary in consistency from that of glucose to that of ordinary coagulated unvulcanized rubber. That material is preferred, however, which is sold under the trade name Vispronal #6 by the Advance Solvents & Chemical Corporation of New York city. This Vispronal #6 has a viscosity of 3 minutes and 40 seconds when determined by the following method. A sample of the polymerized isobutylene contained in a cylinder with an inside diameter of 4 centimeters was heated overnight at a temperature of -140 C. to remove air bubbles. The depth of the liquid in the cylinder was 131/2 centimeters. A steel ball weighing 16.27 grams with a diameter of 1.586 centimeters was then placed on the surface of the liquid and the time required for it to fall to the bottom of the cylinder was measured. For the polymerized isobutylene known as Vispronal #6 this requires 3 minutes and 40 seconds. While a polymerized isobutylene having a Viscosity of this order is preferred, it will be understood that both less viscous and more viscous polymerized isobutylene may be employed. Thus, a polymerized isobutylene believed to have a molecular weight of about 7000 and having a viscosity of 6 seconds, as determined by the above test, has been found satisfactory as have also polymerized isobutylenes of intermediate viscosities, for exarple, of 40-60 seconds, and polymerized isobutylenes having higher viscosities than Vispronal #6. The lower polymers, however, tend to distill out or break down under heating, while the higher polymers are more difficult to apply to the air bag inner surface.

In the preferred form of the invention, however, which comprises the use of the polymerized isobutylene with a non-oxidizable waxy or resinous material, preferably parain, the polymerized isobutylene known as Vispronal #6 has been found very desirable. l/Vhen Vispronal #6 is used the proportions of it and the waxy material may be varied Within wide limits. Thus, from 10 to 90 parts by weight of Vispronal #6 and 90 to 10 parts by weight of, for example, paraffin may be employed in the practice of the invention. A more desirable range of proportions, however, is from 30 to 70 parts by weight of Vispronal #6 and from 70 to 30 parts by weight of paraffin. The most preferred, however, are the compositions which contain from 50 to 60% Vispronal #6 and 50 to 40% paraffin. It will be understood, of course, that these proportions depend upon the consistencies of the polymerized isobutylene and of the relatively non-oxidizable waxy or resinous plasticizing materials and the best proportions of these materials to employ in any case will be determined by actual test.

The compositions consisting of polymerized isobutylene and paraffin, or other relatively nonoxldizable waxy or resinous material, may be conveniently prepared by melting the polymerized isobutylene and then mixing in the paran. It is also possible to first melt the paramn and then add the polymerized isobutylene thereto. Also, a

mixture of the polymerized isobutylene and parain may be heated together until a homogeneous composition is obtained. Generally, as steam pressure of 25 pounds per square inch for a period of one hour is quite sufhcient for the preparation of these compositions.

Further illustrating the invention, a group of 6.00 x 16 curing bags were run in a curing cycle in which the inflating medium was steam under a pressure of pounds per square inch for a predetermined period, followed by air under a pressure of 200 pounds per square inch. Some of the curing bags were each treated with an injection of about .7 pound of a composition consisting of 70 parts by weight of Vispronal #6 and 30 parts by weight of paraffin, the paraffin used melting at a temperature of about 50-60" C. 'Ihese treated bags were run in a curing cycle along with a similar number of curing bags containing no treatment. After 250 heats (this means after the bag had been used for curing 250 tires) those curing bags with no treatment were reduced in volume of rubber about 75% by the corrosive and erosive action of the steam and `air and their vcross-sections were so thin that they had to be replaced by new bags. Those with the composition of :polymerized isobutylene and paraiin ran 420 heats with no noticeable loss in thickness of the bag. Similar and even better results are obtained with a composition consisting by Weight of from 50 to 60% Vispronal #6 and 50 to 40% of paraffin. Also, by adding about 1-6 pound of the composition of polymerized isobutylene and paraffin about every 40 heats still more greatly improved results are obtained. In fact, by this invention the inner surfaces of the curing bag are so protected that when the bag fails, the failure is practically always from some other cause than the wearing `away or oxidation on the inner surface. heretofore this wearing away and oxidation of the inner surface have nearly always been the primary cause of failure of curing bags, it will be apparent that an invention of real merit is provided.

Illustrating the use of polymerized isobutylene containing no non-oxidizable waxy or resinous material, a number of curing bags containing no preservative and a similar number containing on their inner surf-aces a coating of Vispronal #6 were run in a regular curing cycle in which the inflating medium employed in the bags Was a combination of steam and air. The polymerized isobutylene was applied to the inner surfaces of the bags by inserting it into the bags before they 5f were spliced. It was then distributed about their inner surfaces by rolling the bags between pressure rollers prior to the vulcanizing of the bags. These treated curing bags r-an about twice as long before failure as did the untreated bags.

It will be apparent from the foregoing descrip tion that an excellent preserving agent for the surfaces of heated rubber, particularly of curing bags, has been provided. Furthermore, it will be obvious to those skilled in the art that various minor modifications may be made in the invention without departing from the spirit of the invention or from the scope of the appended claims.

What I claim is:

1. A method of preserving curing bags which comprises injecting thereinto a composition comprising polymerized isobutylene.

2. A method of preserving curing bags which comprises injecting thereinto a composition con- When it is considered that f kal All)

sisting of approximately equal parts by weight of polymerized isobutylene and paraffin.

3. In the process of Vulcanizing rubber articles wherein there is employed a rubber former which is distended during the vulcanizing step by means of al combination of steam and an inert gas, the improvement which comprises interiorly supporting the rubber articles during vulcanization by means of an expansble rubber former the inner surface of which is coated with a composition comprising polymerized isobutylene.

4. In the process of Vulcanizing rubber articles wherein there is employed a rubber former which is distended during the vulcanizing step by means of a combination of steam .and an inert gas, the

improvement which comprises interiorly supporting the rubber articles during vulcanization by means of an expansible rubber former the inner surface of which is coated with a composition consisting of polymerized isobutylene and paraln.

5. A method of preserving curing bags which comprises treating the same with a composition containing polymerized is'obutylene and a waxy material.

6. A method of preserving curing bags which comprises treating the s-ame with a composition comprising polymerized isobutylene and paran.

FRANK H. MANCHESTER. 

